A DC/DC converter is used as a power supply for supplying power. The DC/DC converter may be any one of a diode rectification type or a synchronous rectification type. The DC/DC converter of the synchronous rectification type may include a self-driving system. In addition, for the DC/DC converter of the synchronous rectification type, there has been also proposed a driving control system in which a primary controller for controlling a primary switching element controls a secondary switching element for synchronous rectification.